Fibres have been used as optical couplers by removing part of the cladding surrounding the fibre core of a pair of fibres and placing them in contact. The reduced cladding allows coupling between the cores due to their close proximity. One method of forming such a coupler is to make half-coupler blocks by embedding a gently curved fibre in a glass substrate and polishing it to remove a portion of the cladding. A pair of these half-coupler blocks can then be placed together to form an optical coupler. The surfaces of the substrates being flush with the exposed fibre surfaces hold the fibres in the desired position. The manufacturing process is, however, time consuming and needs to be carried out with great care to ensure the correct amount of fibre cladding is removed.